(a) Field of the Invention
The present invention concerns an apparatus for controlling the tension of a filament yarn, and more particularly it pertains to a tension controlling apparatus which is used for a filament yarn as it is taken out from its associated creel of a warper (warper machine) for being subjected to weaving or to warp-knitting, or taken out from a creel to be directed to circular knitting machine, or to shuttleless loom. The apparatus of the present invention is especially useful for controlling the tension of a filament yarn which serves as a warp for being subjected to warp-knitting.
(b) Description of the Prior Art
Warps for being subjected to warp-knitting are prepared usually in such manner that filament yarns of 600-1100 in number are taken out simultaneously from a corresponding number of pirns or supply packages around which the filament yarns are wound, said pirns being mounted on creels of a corresponding number, respectively, and these filament yarns are taken up on a beam at a speed of about 600 m/min. As is well known, the respective filament yarns which are thus taken out from the pirns are collected, by an appropriate converging means such as a reed before being taken up by the beam, to provide a shape as if it were a continuous web consisting of a number of filament yarns each of which is closely positioned to its adjacently positioned yarns. In order to insure that such great number of filament yarns run in a web-like form, it is necessary that the respective filament yarns are taken up under a uniform tension without causing any uneven portions of tension applied to the running filament yarns.
In order to meet such demand, there have been proposed apparatuses intended to control the occurrence of uneven tension of filament yarns being taken up from pirns. For example, there is the so-called washer type tensioning device which is arranged so that a filament yarn is passed from one end to the other end of the device while travelling, in the midway of the course, around portions of circumferences of adjacently positioned two washers supported on corresponding two shafts which can be varied of their positions. The filament yarn is driven to run under a constant tension while being pressed against portions of the circumferences of these washers. Another known tension-providing device is arranged so that a filament yarn is passed between two crossed comb-like members. The angle of crossing of these comb-like members can be adjusted so that the contact area between the filament yarn and the crossed comb-like members through which the filament yarn is passed is adjusted as required, to thereby keep the tension of the running filament yarn constant. However, these known device invariably are based on a same technical concept that the angle of contact formed by the filament yarn passing from the inlet side to the outlet side of the device relative to the guide members is increased to apply a friction pressure to the running filament yarn, to thereby increase, to a certain degree, the tension of the filament yarn taken out from its supply package or pirn. The known tension regulating device which is based on such technical concept as that described above is intended only to control uneveness in the tension and speed with which the filament yarn is taken out. Therefore, such known devices are considered to be significant in that they invariably provide a system for regulating the tension of an individual filament yarn. However, in the warping of warps for use in warp-knitting, the provision of a uniform tension to all of the filament yarns which may be 600 to 1100 in number is a task which is accompanied by a great deal of difficulty. As is well known, the tension regulating devices of the prior art are provided, usually, with means for adjusting the friction pressure applied to the filament yarn. However, it is not an easy task to provide a uniform tension regulating ability to all of as many as 600 to 1100 tension regulating devices in passing as many filament yarns therethrough. Such difficulty may be associated partly with the difficulty in the feasibility of precision with which the respective tension regulating devices are to be manufactured. However, even where the respective tension regulating devices are provided with adjusting means have specific graduations, this will not warrant that the respective filament yarns are taken out and passed to the beam under a uniform tension.
These known tension regulating devices utilizing friction pressure have the following further drawbacks and inconveniences. As is well known, a filament yarn (multifilament yarn) is applied with an oily agent to improve cohesion and smoothness of the filament yarn. However, in case a tension regulating device of the friction pressure type is used for such filament yarn applied with an oily agent, this oily agent and/or a monomer which is residual in the polymer filament yarn is or are caused to gradually depart from the filament yarn due to friction with the surfaces of the guide members, and they naturally begin to adhere to these surfaces thereof. Accordinly, even when, at the start of operation of each tension regulating device, the degree of contact between the filament yarn and its frictional guiding members in each device is set at a uniform level with the exception that the respective filament yarns will be taken out under a predetermined uniform tension, it will be understood that, at time passes, the contact surfaces of the guide members will become soiled by the oily agent of the departing monomer, so that there will appear a change in the angle of contact or in the area of contact between the respective filament yarns and their associating washers, or there will appear unevenesses in the rotation speed of the washers. Under such circumstances, it is no longer possible to keep the respective filament yarns so as to run at a given uniform constant tension continuously for an extended period of time. Not only that, there could appear unevenesses in the tension and elongation of the filament yarn themselves, so that in case the beam around which the filament yarns are wound is subjected to the production of woven fabric or knitted fabric, there arises the fear that rejectable portions such as streaks can develop in the warps. In addition, the development of static electricity and fluffs in the filament yarns due to the friction applied to the yarns on the tension regulating device cannot be avoided.
It is evident that all of these drawbacks and inconveniences of the prior art tension regulating devices are based on the conception to control, by relying on friction pressure, the tension of the filament yarns which are being taken out. If, however, such friction can be removed at least partially, if not all, such drawbacks and inconveniences would be remarkably improved.